1. Field of the Invention
The invention relates to a method and a device for testing an array substrate, and more particularly, to a method and a device for testing an array substrate for a liquid crystal display.
2. Description of the Related Art
As shown in FIGS. 20 and 21, an array substrate for an active matrix type liquid crystal display includes data signal lines 1, scanning signal lines 2 crossing the data signal lines 1, and pixels 3 provided at crossing points of the data signal lines 1 and the scanning signal lines 2. The pixels 3 each include a thin film transistor (TFT) and a pixel capacitor.
Now, a conventional method for testing such an array substrate will be described.
A data signal is supplied to one data signal line 1 and one scanning signal line 2A is driven. In this way, charge is accumulated at a pixel 3 connected to the scanning signal line 2A (data signal writing).
Now, a detection circuit 4 such as an integrator is connected to each of the data signal lines 1, and one scanning signal line is 2A is driven. In this way, charge accumulated at a pixel 3 connected to the scanning signal line 2A is detected by the detection circuit 4 (data signal reading).
The above-described operation is repeated for all the scanning signal lines 2, and the entire array substrate is tested.
By the testing method, the amount of charge detected from a defective pixel is different from the amount of charge detected from a normal pixel, so that whether a pixel 3 is defective (its defectiveness/non-defectiveness) can be determined.
By the testing method, the scanning signal lines 2 are sequentially driven on a one by one basis, and therefore the address of a defective pixel can be specified, but it takes a long period to test all the pixels 3. In the following description, this conventional method will be referred to as “one pixel sequential measuring method.”
Japanese Patent Laid-Open No. 2000-74974 discloses a method of testing an active matrix type liquid crystal display. By the disclosed testing method, two analog switches are simultaneously turned on in order to short-circuit two video buses for supplying a data signal and to detect a line defect. Japanese Patent Laid-Open No. 2000-74974 however does not disclose anything about the simultaneous driving of a plurality of scanning signal lines, which is a characteristic of the present invention.